javascript ("undefined") 中数组的可见性

Question

我试图计算两个矩阵（多维数组）的总和，但收到以下错误消息：

Uncaught TypeError: Cannot set properties of undefined (setting '0')
    at matAdd (matrixCalc.js:28)

当我执行此代码时↓。我不明白为什么“matSum[0][0]”未定义。

// M1 + M2
function matAdd(m1, m2){        
    let matSum = new Array(m1.length);
    for (let i=0; i<m1.length; i++){       //create a blanco-matrix
        matSum=new Array(m1[0].length);
    }
    
    if (m1.length == m2.length && m1[0].length==m2[0].length){
        for (let i=0; i<m1.length; i++){
            for (let j=0; j<m1[0].length; j++){
                matSum[i][j]=m1[i][j]+m2[i][j];                  //HERE THE ERROR OCCURS
            }
        }
    }
    else console.log("Dimension-Error")
    return matSum;
}

the code with line-numbers

感谢您的帮助:)

Answer 1

尝试像这样启动矩阵

function matAdd(m1, m2){        
    let matSum = new Array(m1.length);
    for (let i=0; i<m1.length; i++){       //create a blanco-matrix
        matSum [i] =new Array(m1[0].length); // for each column
    }
    
    if (m1.length == m2.length && m1[0].length==m2[0].length){
        for (let i=0; i<m1.length; i++){
            for (let j=0; j<m1[0].length; j++){
                matSum[i][j]=m1[i][j]+m2[i][j];                  //HERE THE ERROR OCCURS
            }
        }
    }
    else console.log("Dimension-Error")
    return matSum;
}

javascript ("undefined") 中数组的可见性

Visibility of arrays in javascript ("undefined")

javascript

arrays

matrix